A thin-film transistor with an inversely staggered structure in which an amorphous silicon thin film is used for a channel region is known. Since electron mobility of amorphous silicon thin film is small, there is a problem in that a charge mobility in a thin-film transistor is small when the amorphous silicon thin film is used for a channel region.
Therefore, techniques of poly-crystallizing a predetermined area of an amorphous silicon thin film to form a polycrystalline silicon thin film with a high electron mobility by instantaneously heating the predetermined area with a laser beam and using the polycrystalline silicon thin film for a channel region are known.
For example, Japanese Unexamined Patent Application Publication No. 2016-100537 discloses a process of forming an amorphous silicon thin film in a channel region and crystallizing the amorphous silicon thin film to a polycrystalline silicon thin film through melting and solidifying for a short time by irradiating the amorphous silicon thin film with a laser beam such as an excimer laser beam to perform laser annealing. JP '537 also describes that a channel region between a source and a drain of a thin-film transistor can be formed of a polycrystalline silicon thin film with a high electron mobility by performing this process and thus an increase in an operation speed of the transistor can be achieved.
In the thin-film transistor described in JP '537, a channel region between a source and a drain is formed of a single (one) polycrystalline silicon thin film. Accordingly, characteristics of the thin-film transistor depend on the single (one) polycrystalline silicon thin film.
Since the energy density of a laser beam such as an excimer laser beam varies depending on irradiation therewith (shots thereof), the electron mobility of the polycrystalline silicon thin film formed using the laser beam varies. Accordingly, characteristics of a thin-film transistor formed using a polycrystalline silicon thin film also depend on the variation in energy density of the laser beam.
As a result, there is a likelihood that characteristics of a plurality of thin-film transistors included in a glass substrate will vary.
It could therefore be helpful to provide a laser beam irradiation device, a thin-film transistor, and a method of manufacturing a thin-film transistor that can limit a variation in characteristics of a plurality of thin-film transistors included in a glass substrate.
Our laser beam irradiation device may include: a light source that emits a laser beam; and a projection lens that irradiates a plurality of different areas of an amorphous silicon thin film attached to a thin-film transistor with the laser beam, wherein the projection lens irradiates the plurality of different areas of the amorphous silicon thin film with the laser beam such that a source electrode and a drain electrode of the thin-film transistor are connected in parallel to each other by a plurality of channel regions.
In the laser beam irradiation device, the projection lens may perform laser annealing on the amorphous silicon thin film to form a polycrystalline silicon thin film by irradiating the plurality of different areas of the amorphous silicon thin film with the laser beam.
The projection lens may irradiate each of the plurality of different areas with the laser beam a predetermined number of times.
The projection lens may include a plurality of microlenses.
The laser beam irradiation device may further include a plurality of projection masks disposed on the plurality of microlenses and in which areas through which a laser beam is able to be transmitted are disposed to correspond to the plurality of different areas, and the plurality of microlenses may form the polycrystalline silicon thin film by irradiating the plurality of different areas of the amorphous silicon thin film with the laser beam while sequentially switching between the plurality of projection masks.
Our thin-film transistor may include: a source electrode and a drain electrode formed on a glass substrate; and a plurality of channel regions formed between the source electrode and the drain electrode, wherein the plurality of channel regions are formed of a polycrystalline silicon thin film formed by performing laser annealing on an amorphous silicon thin film, and the source electrode and the drain electrode are connected in parallel to each other by the plurality of channel regions.
The plurality of channel regions may have the same width.
Our method of manufacturing a thin-film transistor may include: a first step of forming a polycrystalline silicon thin film by irradiating a first area of an amorphous silicon thin film attached between a source electrode and a drain electrode included in a thin-film transistor with a laser beam; and a second step of forming the polycrystalline silicon thin film by irradiating a second area of the amorphous silicon thin film with the laser beam after irradiating the first area with the laser beam, wherein the second step includes irradiating the second area different from the first area in the amorphous silicon thin film with the laser beam such that the source electrode and the drain electrode are connected in parallel to each other by a plurality of amorphous silicon thin films.
The first and second steps may include forming the polycrystalline silicon thin film by irradiating the amorphous silicon thin film with the laser beam to perform laser annealing on the amorphous silicon thin film.
The first step may include irradiating the first area with the laser beam using a first microlens, and the second step may include irradiating the second area with the laser beam using a second microlens.
The first step may include irradiating the amorphous silicon thin film with the laser beam via a first projection mask in which a transmissive area corresponding to the first area is provided, and the second step may include irradiating the amorphous silicon thin film with the laser beam via a second projection mask in which a transmissive area corresponding to the second area is provided.
It is thus possible to provide a laser beam irradiation device, a thin-film transistor, and a method of manufacturing a thin-film transistor that can limit a variation in characteristics of a plurality of thin-film transistors included in a glass substrate.